How to prevent the injection molding machine head viscose

   By changing the angle of the extrusion profiles drawn from the die head, the position of the glue on the die head can be changed, thereby making it easier to be cleaned. In addition, the die viscose can also be transferred to the product by artificial methods, and then completely removed. For thin plate, you can use automatic scraper scraper scraper.
      However, operators often need to pay such a high price to stop the removal of viscose. After the cleaning is finished, the mold release agent or the silicone resin is applied in the die outlet area, which can reduce the forming speed of the viscose and prolong the interval of two cleaning. In addition, reducing the operating speed of the device can also reduce the die viscose, but this will affect the yield.
      All of these methods are palliatives, the better solution is to find the cause of the formation of viscose.
      The die head adhesive is related to the stress at the exit of die head. At the inner surface of the die, the flow rate of the molten resin is relatively slow, and then suddenly accelerates at the die exit. This acceleration causes stress in the melt, and under the action of stress, the low molecular weight polymer component is separated from the other components in the melt, and is deposited at the exit of the die head to form a viscose. Therefore, the solution to the problem is to reduce the die outlet stress, or to reduce the tendency of the separation of melt components. This may be related to the change of the process material or die. 1. The formation of a thick and loose mold head may be due to the partial foaming of the melt the compatibility of the resin or the excessive stress of the die
      Increasing the temperature of the die and melt is one of the methods to reduce the exit pressure of the die, but it may lead to additional degradation, which leads to the increase of low molecular weight components. Therefore, it is necessary to adjust the temperature of melt and die. But note that, sometimes, the low die temperature, the resin may form a slow velocity of flow in the die surface layer of cold flow, the main flow layer and the resin cold from each other, and eventually lead to the formation of viscose.
      Through the simulation of the die flow to study the resin in the outlet of the die stress changes, this stress will eventually lead to the generation of die viscose (pictures from Compuplast company) to set the temperature of the die head, first to determine the true temperature of the melt. Since the standard melt thermocouple often produces errors, it is necessary to manually measure the melt temperature. Although this approach is difficult, but it is necessary to find the cause of the fault. In addition, because the surface temperature at the die exit is much lower than the temperature of the die head, the surface thermocouple should be used as the exit temperature.
      The air outlet of the die head can reduce and control the generation of viscose, and can also be used to remove various kinds of flue gas and condensable gas from the die head. In addition, the blast also helps to cool the mold head of viscose, so that it is not easy oxidation black. N2 can also be used to prevent oxidation. It should be noted, however, that it is not too cold or too low to reduce the die temperature.
      Change die viscose raw material may make different forms, some thick and sticky, some thick loose. A thin, sticky adhesive is formed at the exit of the die head and is condensed on the surface of the die head. Thick and loose viscose is usually caused by the partial foaming of the melt, the compatibility problem or the internal pressure of the die head. Therefore, in the extrusion, the resin should avoid excessive humidity or degradation, as well as possible melt rupture or improper exhaust.
      There are some suppliers of resins that produce more adhesive than those from other sources, even if they have exactly the same technical specifications. When the head of viscose, try to use other suppliers of similar grades of resin, if the problem has improved viscose, the initial resin may be a problem in performance.
      Resins from different suppliers may have similar shear viscosity, but have very different elongational viscosity. If there is no difference in performance, it is possible to test the viscosity. The higher the viscosity of the resin may be due to die outlet pressure becomes larger and more viscose.
      At the same time, the resin with higher expansion of the mold has a higher rate of the formation of the die head. When the resin has a narrow molecular weight distribution, the expansion of the mold may be lower, but this does not necessarily mean that the formation of less viscose. In general, the resin with narrow molecular weight distribution is difficult to be processed, and the low molecular weight components may be produced, which eventually lead to the formation of the viscose.
      For the regeneration of resin, usually containing a low molecular weight due to thermal degradation of the previous processing. In this regard, additives can be added to inhibit degradation, or the use of chain extender can cause the degradation of components to be re polymerization. If these do not work, they will not be suitable for use.
      In some cases, the addition of lubricants helps to reduce the amount of viscose, but too much lubricant may also increase the production of viscose. The chemical compatibility of different components in the formula is one of the important factors affecting the viscose. For example, when highly incompatible polymers melt and mix together, the extreme case of viscose. In this case, the use of compatibilizer will help ease the formation of viscose. In addition, the addition of a small amount of fluoropolymer processing aids can also reduce the die exit geometry of the die exit strain gauge 3
      For rapid oxidation, variable die viscose type yellow or black, can add antioxidant in the formula. Although this does not solve the problem of die adhesive, the adhesive on the product becomes invisible.
      Changing the mold head on the surface of the mold coated with fluoropolymer, such as PTFE, to a certain extent to prevent the formation of viscose. The more effective way is to use the metal coating, so that the fluorine polymer into the mold head, to reduce the stress of the die outlet.
      On the other hand, the flow simulation of the die head has been successfully applied to solve the problem of die adhesive. By simulating the flow state of the resin at the die head, it can be used to study the forming reason of the die exit stress, and to evaluate the effect of changing the geometry of the die exit on the adhesive.
      It is a widely used method to improve the die exit geometry to reduce stress. Some die shape has been export producers and processors of resin applied for patent protection. It can reduce the improved die outlet die viscose production include: square, ladder shaped export sharp sharp sharp export exports, round export, outward stepped exit, inward outward and funnel-shaped outlet.
      In addition, by increasing the length of the die forming section, thereby reducing the resin at the exit of the mold head changes, but also help to reduce the die outlet stress.